Amplifying system



Dec. 19, 1933. .1. D. MARSHALL AMPLIFYING SYSTEI Filed April 14. 1927 @Q am bm o* 0. 'v @mi ,1 T\. m .lm mw n @M 4W e h n m m S @m 3 m M.. @n m D 3 Om SA? 2 J -T l f i Q 1T@ mw H n u... mw n mm@ w: L n IW' N. .NHT L ON. \1@:

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Patented Dec. 19, 1933 UNITED STATES TENT OFFICE 2 Claims.

My invention relates to amplifying systems used in radio circuits and has for its object to pro# vide a system whereby maximum amplification may be had pertube at a minimum current consumption.

Another object of the invention resides in providing an amplifying system in which the tubes are caused to function on the proper portions of their characteristic curves and in which the transformers operated thereby are caused to operate at maximum efficiency.

An object of the invention resides in providing a transformer having a primary and an input tubetherefor, and in providing a circuit for op erating said transformer primary connected to the plate of said tube and having a return path to the filament thereof, and a second circuit ccnnected to the plate and filament of said tube including a resistance and source lof connected in series therein. Y

A feature of the invention resides in including in said transformer primary circuit a condenser connected in series with said transformerprimary for diverting the direct current produced by said source of B voltage'from said transformer primary circuit.

Other objects of` the invention reside in the novel combination and arrangement of parts hereinafter described, illustrated and claimed.

In the drawing:

Fig. 1 is a wiring diagram illustrating the application of my invention to an audio frequency amplifying system for radio receivers.

Fig. 2 is a Wiring diagram of a modification of the system shown in 1.

Fig. 3 a wiring diagram illustrating the ap` plication of my invention to a radio frequency amplifying system.

Fig. 4 is a wiring diagram of a modification of the system shown in lig. 3.

Fig. 5 is a wringdiagram similar toFig. 3, showing another application of the invention to radio frequency amplifying systems.

Fig. 6 is a` Wiringdiagram illustrating the application of ,inventionv to aregenerative detectcr for use in conjunction with radio receiving apparatus.

Figlf is a Wiring diagramef. alcompletefive tube radio receiving set illustrating the application of my invention to all ciV the transformers thereof.

In radio receiving apparatus considerabledifnculty encountered in amplifying both the radio and audio frequency currents, due to the inability tc secure sufiicient amplification per stage B voltage (C1. vs -171) without introducing distortion of the signal, oscillation of the tubes, excessive current consumption, shortening of tube life, or other disadvantages. My invention overcomes these difficulties in a manner which will be presently described.

For the purpose of explaining the theory of my invention I have assumed that radio frequency currents Yin flowing through the grid circuit of the various radio tubes serve to simply change the impedance between the plate and cathode of the tube instead of going into the ionization theory of the operation of a three elementl radio tube. By means of this assumption which has been previously recognized as apt, the

explanation of the theory and operation of my invention becomes very simple.

In Fig. 1, I have shown myA invention as applied to a stage of'audio frequency amplification. In this diagram is illustrated an input tube 1,0 having a grid 11, a plate 12 and a filament 13 in conjunction with an output tube 14 having a. grid 15, plate A16 and filament 17. The usual Abattery circuit 26 is employed, which includes an fA battery 27 or other suitable source of A current andserves to heat the filaments 13 and 17 of tubes-10 and 14 in the usual manner. IIfhe tube is connected to the primary 18 of an audio frequency transformer 19 in a manner to be presently described, while the secondary 20 of said transformer is connected to the grid .15 and filament 17 of the` output tube 14 in the usual manner, In my invention I'employ in conjunction with the transformer 19 a separate circuit 21 which is connected to plate 12 of the input tube and has a return to the filament 13 through one of the leads of the A battery circuit 26, and which contains the usual B battery 22 or other suitable supply of B voltage, and a resistance 23.V This circuit is shunted by a circuit 24 which is'also `connected to the plate 12 and to the filament 13, which circuitincludes the primary 18 of transformer 19, and a condenser 25 connected in series therewith. For the sake of clearness, the stage of audio amplification has been shown isolated from the remainder of the receiving circuit, the input to the tube 10 and the output from the tubef14 not having been shown in this dia.- gram, though it can readily be comprehended that the stage of amplification may be added wherever' desired, as will become apparent with the circuitv illustrated in Fig. 7 showing a complete radio receiver. vWhere a battery operated tube is employed the filament forms the cathode or return element for the circuit connected to the plate. It can, however, be comprehended usual manner.

that the same results are produced where a tube having a separate cathode and a heater heated by a separate circuit is used. The present invention contemplates any equivalent type of tube and inthe description, the word filament is used as referring to the cathode or return element of the plate circuit as well as to the heating element.

The operation of the amplifying system shown in Fig. 1 is as follows: By means of the B battery 22 and the resistance 23, a difference in potential occurs across the impedance between the filament 13 and plate 12, which for the sake of convenience I will designate as X, and the resistance 23. This difference in potential is divided up between the two impedances in accordance with their relative values. Due to the said B battery, a current flows through the circuit 21, which without the influence of radio frequency currents would be a direct current of fixed value. Upon impressing a pulsating radio frequency potential across the grid 11 and filament 13, the impedance X between the grid 13 and plate 12 is caused to vary in accordance with the pulsations of the radio frequency currents, as previously mentioned. Upon varying this impedance, the difference in potential across the same is Isimilarly caused to vary, due to the fact that the total voltage from the B battery remains constant and the resistance 23 remains unvaried during the operation of the system. This variation in the difference in potential is impressed upon the primary 18 of transformer 19 which is directly connected across the plate l2 and lament 13 through circuit 24, which variations in difference of potential are transformed to higher potential values by the transformer and are transferred to the tube 14 and amplied in `the Through the agency of the condenser 25, the direct current from the B battery 22 flowing through the circuit 21 is diverted from the circuit 24 so that only the pulsating current occasioned through the variations of the difference in potential between the filament 13 1"5A and plate 12 pass through the same. This has the effect of causing the transformer 19 to function solely for the purpose of transforming the alternating currents occasioned by the variations in the impedance and not the variable direct through the primary of said transformer. 553:

current from the B battery. For this reason a much lower flux density occurs in the field of the said transformer than would be the case were the entire current from the B battery `directed This permits of operating the transformer at a lower flux density than is otherwise possible and ofy designing transformers for use in my system of arnplincation with a smaller cross section of core.

Although I have shown the condenser 25 as positioned in the upper leg of circuit 24, yet the same may be readily positioned in the lower leg of said circuit or the capacity divided and a portion placed in each leg, thereby completely isolating the primary of the transformer from direct currents passing through the circuit 21.

Inasmuch as the resistance 23 connected in series with the B battery 22 remains fixed throughout the operation of the tube, whenever the impedance X is varied due tothe action of the tube, the difference in potential or the drop across this resistance varies in accordance with the drop across the impedance X. For this reason the circuit 24 containing the transformer primary 18 may be arranged to shunt the resistance 23 instead of the impedance X. The method of connecting up the apparatus to produce this result is shown in Fig. 2, the circuit therein illustrated being identical with that shown in Fig. 1, except that the lower lead. 28 of circuit 24 is connected to the circuit 2l between the B battery 22 and the resistance 23 instead of directly to the lead running from the tube filament. The operation in this form of the invention is substantially the same as that illustrated in Fig. 1, depending upon the value of the B battery Voltage and the relative values of the impedance X and resistance 23.

In Fig. 3 I have shown a wiring diagram illustrating the application of my invention to one stage of a radio frequency amplification. In this diagram I show an input tube 29 having a grid 30, a plate 31 and a filament 32, together with an output tube 33 having a grid 34, plate 35 and filament 36. For heating the filaments 32 and 36 of these two tubes, I employ the usual A battery circuit 41 and an A battery 42, or any other source of A current, which operates in the usual manner. In conjunction with the tubes 29 and 33, a radio frequency transformer 37 is employed having a primary 33 and a secondary 39, which transformer may be of the air cored type, if desired, the primary and secondary being independently wound and positioned relative to one another in any desired relation such as is now in common use in radio frequency transformers.

With this form of the invention, I employ a circuit 40 which contains the transformer primary 38 and is connected to the plate 31 and to one of the leads of the circuit 41 providing a return to the filament 32. former 37 is connected by means of a circuit 43 to the grid 34 and filament 36 of the output tube 33, which secondary is shunted by a tuning condenser 44 in a manner well known in the art. In addition to the circuit 40, an auxiliary circuit 45 is employed which is connected at one end to the plate 3l and at its other Vend to the filament 32 of the tube 29. This circuit is similar to the circuit 21 of the form of the invention shown in Fig. 1 and includes a resistance 46 and a B battery 47, the same as said circuit. Within this circuit is placed a condenser 43 similar to the condenser 25 which diverts the direct current produced by the B battery 4'7 and circuit 45 away from the primary 38.

The operation of the invention when used in conjunction with a radio frequency transformer is similar to that used in an audio .frequency transformer, the variations in the voltage across the impedance between the plate 31 and ilacase were the said transformer directly connected to receive the current flowing through the B battery, which allows the application of a greater degree of regeneration as will be presently eX- plained, and reduces the resistance of the circuit to the flowof radio frequency currents.

In Fig. 4 I have shown a circuit illustrating the application of my invention to radio frequency amplification showing a transformer, the same as that illustrated in Fig. 3, being connected across the resistance 46 the same as in Fig. 2. The

The secondary 39 of transoperation of this circuit is the same as that shown in Fig. 2 excepting that the circuit is used in conjunction with the radio frequency amplification instead of audio frequency amplification.

The application of my invention to a different form of transformer used forA radio frequency amplification is illustrated in Fig. 5. In this figure I have shown an input tube 49 having a grid 50, plate 51 and filament 52, together with an output tube 53 having a grid 54, a plate 55 and a filament 56. The filaments'52 and 56 of these two tubes are heated through a filament circuit 57 operated by an A battery 58 or any other suitable source of A current in the ordinary manner. In conjunction with these tubes I have shown a transformer or coupling coil 59 formed by means of a single continuous winding having a tap intermediate the ends thereof indicated at 60 to form a primary 61 and a secondary 62 arranged both in inductive relation to one another and being electrically connected together. This coil is connected in a circuit 63 which is connected at one end to the grid 54 and the other end to the filament 56 of the output tube 53. Acondenser 165 shunts the secondary 162 and serves to tune the circuit. The tap 60 of the transformer is connected in a circuit 64 including a condenser 164 which in turn is connected to the plate 51 and finds a path through the primary 61 and returns to the filament 52 of tube 49 through the lower leg of the circuit 63 and one of the leads of the A battery circuit 57. In conjunction with this circuit an auxiliary circuit 65 is employed which is similar to the circuits 45 and 21 and contains the B battery 66 of other source of B voltage, and a resistance 67.

The theory and operation of this circuit is identical with that of the circuit illustrated in Fig. 3, except that a slightly different type of transformer has been used. I find, however, that with my particular invention the output from the input tube may be applied to the tap 60 .of the transformer 59 Without affecting the stability of the system, thereby greatly simplifying the construction of the transformer and permitting of closer coupling than is usually customary. Although I have specified the primary 61 and `secondary 62 of transformer 59 are formed by taking off a tap 60 therefrom, yet it can be readily comprehended that separate coils can be used and the ends thereof connected together and to a single conductorforming a part of the circuit 64.

If desired, my invention may be used to follow theusual detector tube in the ordinary radio receiving circuit. The application of my invention to this particular use is shown in Fig. 6. In this figure I have illustrated a detector tube 67 having a grid 68, plate 69 and filament 70, together with an amplifying tube 71, having a grid 72, plate 73 and filament 74. Both the filaments and 74 of the tubes 67 and 71 are heated through an A battery circuit 70 which is en-v. ergized by means of an A battery 80, or other suitable source of A current. An audio frequency transformer 75 is used in conjunction with these tubes consisting of a primary 76 and a secondary 77. The secondary 77 of transformer 75 is included in a circuit 78which isV connected to the` grid 72 and to the filament 74 of tube 71;

The primary 76 of this transformer is connected in series with a condenser 163 in a.

former or coupler 82 has beenrshown having a primary 83 and a secondary 84. This transformer may be of any desired type and the secondary 84 thereof is interposed in a circuit 85 which is connected to the grid 68 and through the usual grid condenser and leak 160 to filament 70 of tube 67, the said secondary being tuned by a shunted tuning condenser 86, as is now well known in the art. In this particular case the Vprimary 83 of transformer 82 has not been shown as connected to any source of radio frequency currents, though it can be Yreadily comprehended that the same can be connected to an aerial andl ground or may receive the output from a previous amplifying tube in a radio receiving set. For providing regeneration in conjunction with the transformer 82, a tickler coil 87 is employed which is arranged in inductive relation to the transformer 82. This tickler coil is connected in a circuit 88 connected to the plate 69 and lament 70 of tube 67 and may be of the rotary type or may have connected in series with it in said circuit a Variable condenser 89 for the purpose of controlling the degree of regeneration impressed upon the transformer 82. g

the transformer primary 76 is diverted and sent through the tickler coil 87 where the same again passes through the tube and is further amplied in the customary manner. The placing of the variable condenser 89 in the circuit 88 prevents the flow of direct currents through this circuit producing as weak a field in the tickler.

coil 87 as in the primary and secondary of the transformer 82, thereby in nowise affecting the operation of the system or detracting from the advantages thereof.

In the description of my invention I have referred to the coils used in both the audio frequency and radio frequency circuits as transformers, which term I have used as a broad term for including both radio frequency and audio frequency transformers, couplers, coils, or tuning device in which a primary and secondary are to be found, having inductive relation with one another and adapted to transfer electrical energy from one to the other, and I have further used the same term to include both air cored or iron cored transformers.

The advantages of my invention are as follows:

The advantages obtained through the use of resistance couplings and transformer couplings are simultaneously combined with my invention to give a far superior performance than wouldl be possible with either system used alone. Greater voltage amplification per stage can be secured with my invention with less plate power measured in Watts than with any other system of'amplication. While a relatively high plateV voltage is most advantageously utilized, yet the resistance in series with the source of B current maybe made sufficiently high to cut down a the current consumption, at the same time providing sufcient drop in'potential across the impedance from the plate to the filament to operate the tube at a favorable point on its characteristic curve. Y Byv eliminating the grid leak utilized in resistance couplings in accordance with the common practice the grid of the tube following the resistance circuit may be kept sufficiently negative to eliminate the C battery or to greatly reduce the C battery voltage required. I have found by actual test that except for the last audio stage, splendid results withY minimum possible distortion can be secured at a minimum B battery consumption without the use of C batteries. Due to reduced current flow the life of the tubes used in my invention is greatly increased. The application and control of regeneration used in conjunction with my invention is greatly simplified due to the elimination of plate potental and direct currents from the transformer primary. Grid bias of such values as to reduce the tendency to oscillate may be readily applied to the grids of the tubes without high current consumption, reduction of tube life or distortion. The use of resistance in the plate circuit such as 45 in Figs. 3 and 4 shunting the primary of radio frequency transformer reducesthe tendency of tubes to go into oscillation abruptly even though no other neutralizing device is employed. Furthermore, better detector action can be secured by adjusting the resistance to cause the tube to perform along the most favorable portion of the characteristic curve thereof. When the invention is used in conjunction with audio frequency amplification, the direct currents are diverted from the transformer eliminating core saturation bringing the flux density down to a value commensurate with the eilicient operation of the transformer, thereby permitting of a design of transformer with less core cross section. In addition, the placing of the condenser in series with the reactance of the transformer primary causes a more flattened characteristic curve for the amplification Aof the combination, whereby the condenser serves to regulate the value of the lower audio frequency while the reactances of the transformer serve to regulate the higher frequencies. In addition, higher f ratios of transformer windings may be employed due to the absence of core saturation and less capacity losses between primary and secondary, without causing distortion of the signals. In the use of my invention in its various aspects and particularly in conjunction with audio frequency amplification, a pure, sweet, mellow tone is secured with a greater Volume than could be had with the ordinary iron cored transformer system of audio amplification. In this way, both the advantages of the transformer and resistance system of coupling are utilized with the additional advantage of greater amplification and less current consumption.

For the purpose of illustrating a practical embodiment of my invention, I have shown a circuit in Fig. 7 which illustrates a number of different applications of my invention. This circuit includes five tubes 100, 101, 102, 103, and 104. Of these tubes tube 102 is a detector tube, while tubes 103 and 104 are audio frequency amplifying tubes. The tube 100 serves as a radio frequency amplifying tube, while the tube 101 augments the action of the tube 100 and serves solely for the purpose of controlling regeneration impressed upon the antenna coupling coil or transformer. In this circuit an antenna coupling coil 105 and a radio frequency transformerl 106 are employed. Both of these coils or transformers may be of the type illustrated in Fig. 5.' The coupler 105 consists of a primary 107 and a secondary 108, while the transformer 106 consists of aprimary 109 and a secondary 110. In additionto the primaries and secondaries the coupling coil 105 is provided with a fixed tickler 111 and the transformer 106 with a fixed tickler 112.

All of the filaments of the Various tubes of the circuit are heated through an A battery lead 114 connected to an A battery 116 and a common A and B battery lead 115, while B battery current is suppliedto the various tubes through the common A and B battery lead 115 and a lead 118 from a B battery 119. The primary 107 of coupler 105 is directly connected to an aerial 113 andto. ground as indicated at 120, the lead 144 being also connected to ground. The secondary 108 of transformer 105 which includes the primary 107 is connected through a lead 156 to the negative A battery lead 114 and to both of the grids of tubes 100 and 101 in parallel, said secondary being shunted by a variable tuning condenser 121 in a circuit 157. In addition to those circuits the tickler coil 11 employed with the coupler 105 is connected in series with a variable condenser 122 in a circuit 123, which circuit is directly connected to the plate of the augmenting tube 101. In a similar manner the detector tube 102 which is provided in its grid-circuit 158 with a grid leak resistance and condenser indicated at. 124, is connected to the secondary 110 of transformer 106, while the output of the tube 100 is connected through a lead 159 to the primary of said transformer in the same manner as the output from the aerial and ground connection of coupler 105. In this case, howeven'the tickler 112 is fed from the detector tube 102 instead of from a separate augmenting tube as in the case or" the radio frequency amplifying tube 100, the said tickler being connected in series with a variable condenser 125 in a circuit 126 connected to the plate of said tube 102. In this circuit, a tuning condenser 127 similar to condenser 121 and connected in a circuit 160 is employed for tuning the secondary of transformer 106.

For the purpose of neutralizing the radio frequency tube 100 and preventing 11e-radiation, the system may be neutralized by any of the well known methods. I have found that the so-called Rcberts system of neutralization operates admirably. with my invention and have illustrated this particular type of neutralization in this circuit. For this purposean auxiliary coil 128 identical with the primary 109 of transformer 106 is employed, which is connected to said primary and in series with a neutralizing condenser 129 in a circuit 130 connected to the grids of the tubes 100 and 101. By properly adjusting this neutralizing condenser re-radiation is prevented, permitting of the use of regeneration in both the radio frequency and detector tube circuits without molesting the public.

InV conjunction with the augmenter tube 101 I employ a circuit 131 connected between the B battery plus lead 118 and the plate of said tube. This circuit contains a resistance 132 which functions in much the same manner as the type of circuit shown in Fig. 6. including a resistance 134 is connected across the plate of tube 100 and B battery lead 118 and operates as described in conjunction with the invention yasV disclosedin Fig. 5. In addition a condenser 161 is placed in the circuit 159 in series with the primary 109. This much of the circuit comprises the detecting and radio frequency elements of the same.V

lIn the audio frequency part of the circuit illustrated in Fig. 7 the two tubes 103 and 104 are A similar circuit 133 used. In conjunction with these tubes are employed rtwo audio 'frequency transformers 135 and 136, which are connected to their respectivev input and output tubes in identically the same manner as shown in Fig. 1. The transformer 135 is constructed with a primary 139 and a secondary 140. The secondary 138 of transformer 135 is connected in a circuit 141 between the grid of tube 103 and the A batterylead 114, while the secondary 140 of transformer 136 is similarly connected in a circuit 142 to the grid of tube 104 and the same A battery lead. The primary 137 of transformer 135 is connected in a circuit 143 to the plate of tube 102 and to the negative A battery lead 114, while the primary 139 of transformer 136 is similarly connected in a circuit 144 to the plate of tube 103 and the same A battery lead. In conjunction with the two circuits 143 and 144 I provide the two auxiliary circuits 145 and 146 which are connected between the plates of the respective tubes 102 and 103 and the positive B battery lead 118. These circuits contain resistances 147 and 148 similar to the circuit shown in Fig. l, While the circuits 143 and 144 have condensers 149 and 150 therein for diverting the direct currents from the transformer primaries. A jack 180 placed in the plate circuit 157 of the last tube 104 is connected to a suitable loud speaker, or other output device, in the usual manner.

By making the resistance 132 variable the regeneration applied to the coupling coil 105 from the augmenter tube 101 may be varied so that a fixed tickler 111 can be employed, the said resistance being set so that the maximum permissible regeneration is had at the higher wave lengths and by mounting condensers 121 and 122 on the same shaft, squealing or howling is prevented. Similarly, the resistance 134 may be made variable which when so constructed provides a splendid volume control for the receiver. The condenser 125 for controlling the regeneration through the tickler coil 112 may be likewise mounted on a common shaft with the condenser 127 so as to give the maximum regeneration at the higher wave lengths. When using a fixed tickler as the coilj1l2 an additional manually controlled condenser 153 may be employed, which is connected in parallel with the condenser 125. This condenser need only be adjusted to control the regeneration when the receiver is rst set up and need not be further adjusted unless it is desired to boost theregeneration to the extreme maximum in the event that especially weak signals are being received.

The values for the different resistances, inductances, and capacities used in this circuit may be such as are now in common use. The transg formers` 105 and 106 may be ofr any ordinary air cored type while c'ondenserslZl, 123, 125 and 127 may be of such valueas to bring the respective circuits in resonances anywhere from 200 .to 600 meters when the receiving set is used for broadcast reception. When vthe receiving apparatus as illustrated in Fig. 7 is used for broad-v I have found by actual experiment that the values quoted give splendid results in the particular circuit shown while considerable ranges of value may be adopted without affecting the tone quality or distorting the signals. In this particular circuit, I have used type 199 tubes for the rst four tubes and a type 120 tube for the last or output tube employing a B battery voltage of 135 Volts. With this Voltage the plate of the last tube 104 is directly connected across the B battery, while all of the supplemental resistance circuits of my invention are directly connected across the same B battery lead, thereby eliminating the neccesity of several B battery leads. I have found that the higher the voltage of the B battery,the greater the output of the receiver, though with increase of B battery voltage it becomes necessary to correspondingly increase the value of the various resistances. In case the greater B battery voltage is employed than that for which the output tube is designed, a suitable resistance must be placed in the output circuit to bring the B battery voltage down to the proper value and supply the speaker through a condenser. Although the operation of the receiver is satisfactory without the use of C" batteries, yet the addition of C batteries improves the operation, particularly in the last stage where the type 120 tube is used and any considerable volume is desired from the output circuit. When using a C battery in the last stage the same is inserted as indicated at 152 in the circuit 132 connected to the grid of tube 104.

Although I have given specific values to the resistances employed in my invention in the particular circuit illustrated in Fig. ,7, yet it can be comprehended that the Values may be varied considerably depending upon the B battery voltage, the particular tubes and the transformers, and coupling coils used in connection with the same and that further, the arrangement of the condensers employed in the transformer primary circuits may be altered or split up, or other changes made without departing from the spirit of the invention within the scope of the following claims.

What I claim desired to be covered by Letters Patent is:.

l. In combination with an electron discharge tube, a pair of inductances connected together, a circuit including the plate and cathode of said tube, a resistance and source of B voltage in series in said circuit, a second circuit connected to said plate and having a return to said cathode, said second circuit including one of said inductances and having a condenser in series therewith and an input circuit for a following tube including both of said inductances.

2. In combination with an electron discharge tube, a transformer having a continuous Winding provided with a tap, a circuit including the plate and cathode of said tube, a resistance and source of B voltage in series in said circuit, a conductor between said plate and tap, a second conductor connected to one end of said winding and to the cathode of said tube, a condenser in one of said conductors and a circuit including the entire winding of said transformer.

JAMES D. MARSHALL. 

